Unix Virtual Memory Management

Memory Allocation
Handed out by kernel
Easy to enforce global resource limits

Low Level Management
Completely inside the kernel
Used by nearly all subsystems
Uses many subsystems
Boundaries are often unclear; no formal protocols

Paging Policy
Does not consult user-space applications
Applies a global policy, typically an approximation of LRU, least recently used
Very inefficient for many classes of applications
Databases
Garbage collectors
Media applications

Paging
Kernel sends pages to the appropriate backing store
No trust issues: all functionality and decisions in the kernel